Myocarditis
in Childrenadapted from the web site of the
Cincinnati Children's Heat Center and posted 07-07-05 on kidsgrowth.com

What is
myocarditis?

Myocarditis
is an inflammation of the myocardium, the thick muscular layer
making up the major portion of your heart. When this condition
is uncommon in children, it can cause pumping action of
your child's heart to weaken. This in turn makes the heart
unable to supply the rest of your body with enough oxygen-rich
blood. Clots can form as well, potentially leading to a stroke
or heart attack. There are many
causes of myocarditis including infections, medications,
chemicals, radiation, and certain diseases that cause
inflammation in many different organs of the body. In most
children, myocarditis is most often triggered by an infection,
usually viral, involving the heart.

What causes
Myocarditis in children?

Years
ago, rheumatic fever was a common cause of myocarditis. But
today, there are usually other reasons for myocarditis, most
often when it develops secondary to an underlying infection
caused by:

Viruses.
The virus most often associated with myocarditis is
coxsackievirus B. But adenovirus, parvovirus B19,
echovirus, influenza virus, Epstein-Barr virus and rubella
virus are other viral causes of myocarditis. HIV, the
virus that causes AIDS, can directly infiltrate the heart
muscle.

Bacteria.
These include Staphylococcus aureus, which can
also cause an infection of the heart valves called
endocarditis.and a tick-borne bacterium called Borrelia
burgdorferi, which is responsible for Lyme disease.
Rarely, bacteria such as those causing the tick-borne
illness Lyme disease can cause myocarditis. It is
important to recognize that even though a child may have
develop Lyme Disease it is rare for them to develop
myocarditis. Myocarditis also occurs in more than
one-fourth of all people with diphtheria, a disease caused
by the bacterium Corynebacterium diphtheriae.

Parasites.
Among these are such parasites as Trypanosoma cruzi
and toxoplasma, including some that are transmitted by
insects and can cause a condition called Chagas' disease.
This disease is much more prevalent in Central and South
America than in the United States, but it can occur in
travelers to and in immigrants from that part of the
world.

Fungi.
These causes include candida, aspergillus and histoplasma.
They are rare causes of myocarditis.

When an infectious organism is
the cause of the myocarditis, the initial event that must
occur is infection of the heart by that organism. The child's
immune system is then called upon to eliminate the infection.
In some children, this response is over-aggressive so that in
addition to destroying the infecting organism, the heart cells
themselves may be damaged.

Most of the damage to the heart
seen is a result of the body's immune reaction to the
infectious organism, not the organism itself. It is unclear
why this happens in some children. The abnormal immune
response may be confined to a small area or involve a large
portion of muscle tissue. The severity of symptoms is often
related to how much heart muscle is involved.

Damaged muscle cells may heal
over time or there may be cell death followed by scar
formation. If this process is extensive and a large portion of
the heart is involved, the ability of the heart to pump blood
is impaired. . There is thickening and swelling of the heart
muscle. All four chambers of the heart may be affected and
become enlarged.

As
a result, the important organs and tissues in the body are
deprived of oxygen and nutrients and cannot eliminate waste
products. This is often referred to as congestive heart
failure.

Myocarditis also sometimes
occurs when a child is exposed to:

Certain
chemicals. These may include substances such as
arsenic and hydrocarbons.

Medications
that may cause an allergic or toxic reaction.
These include antibiotics such as penicillin and
streptomycin and anti-epilepsy drugs such as phenytoin and
carbamazepine, as well as some illegal substances, such as
cocaine.

Systemic
diseases. These include lupus, other connective
tissue disorders, inflammation of blood vessels (vasculitis),
and rare inflammatory conditions such as Wegener's
granulomatosis.

Symptoms of
myocarditis

The
signs and symptoms of myocarditis may vary, depending on the
cause and the severity of the disease. The symptoms of
myocarditis are usually subtle, making the diagnosis
difficult, or the child may experience overt symptoms of heart
failure. Clinical experience has shown the severity of
symptoms or illness is dependent upon the age of the child.Children
over 2 years of age may be less symptomatic than newborns and
infants who are usually more severely affected. This is
thought to be due to the immaturity of a baby's immune system.

The most common signs and
symptoms include:

Vague chest pains

A rapid or abnormal
heartbeat (arrhythmia)

Shortness of breath,
particularly during physical activity, or complaints of
palpitations (skipped or missed heart beats)

Fluid retention with
swelling of your child's legs, ankles and feet

Joint pain

Fever

Fatigue

High temperature

Loss of appetite

Breathing difficulties

Bluish or grayish
discoloration of the skin

Other signs and symptoms may
occasionally occur as well, such as:

Fainting
or a sudden loss of consciousness, which may be associated
with irregular heart rhythms

A
decline in the volume urine

Other
symptoms associated with a viral infection, such as a
headache, body aches, a fever and a sore throat

Diagnosis of
myocarditis

Unfortunately, to
the frustration of parents and doctors, there is no specific
test for myocarditis. It is mostly a clinical diagnosis;
therefore the physician must rely on the history provided by
the family and physical examination of the child.

There are many tests that can
be performed that help support a suspected diagnosis of
myocarditis. The most common test is a chest X-ray. Often the
heart size is enlarged, the blood vessels of the lungs are
prominent, and fluid may enter the lungs.

An electrocardiogram can also
give helpful clues if the diagnosis is suspected; however, the
findings may be non-specific.

An echocardiogram or heart
ultrasound can be used to assess heart size and overall
function which helps confirm the clinical diagnosis as well as
rule out the presence of blood clots within the heart chambers
which can form due to poor heart function.

Blood
tests measure white and red blood counts, as well as levels of
certain enzymes that indicate damage to your heart muscle.
Blood tests can also detect antibodies against viruses and
other organisms that may indicate a myocarditis-related
infection.

The most precise way to make
the diagnosis of myocarditis relies on heart biopsy obtained
during a cardiac catheterization. This involves the use of a
long catheter that is passed up a large blood vessel in the
leg. Once the catheter is in the heart, a tiny piece of heart
muscle is obtained and sent to the pathologist for inspection
under the microscope.Results
vary but the diagnosis of myocarditis is made by this method
up to 65 percent of the time. The results of the biopsy are
not 100 percent because the areas of the heart affected by the
inflammation are often patchy and may be missed.

Treatment of
myocarditis

The inflammation
that occurs will usually resolve on its own. There is no cure
for myocarditis. In general, the goal of medical therapy is to
support the heart function so that adequate blood circulation
is maintained.

Medications that are able to
help the heart work more either by regulating the blood
pressure or by improving the ability of the heart to pump
blood are the first line of treatment.One
or more of these medications may be considered depending upon
the severity of the myocarditis. In addition, a diuretic is
commonly used to help clear excess fluid from the lungs or
other body tissues.There
are also medications that are designed to decrease the
abnormal immune response, which are currently under
investigation.One drug
frequently used is called intravenous immunoglobulin (IVIG)
which consists of purified antibodies, the substances that the
body's immune cells produce to fight infection. Its mechanism
of action is unclear but it has been shown to slow down the
inflammatory process.

Most children diagnosed with
myocarditis are admitted to an intensive care unit for initial
management.It is important
for the child to be placed on bed rest. There is evidence to
suggest that strenuous activity may be harmful to the heart
during the recovery period.

Depending upon the severity of
the myocarditis, this may mean that physical activity is
restricted for weeks to months. The child's physical activity
should be slowly increased over time.

The good news is that
approximately two-thirds of the children, with appropriate
medical management, will have a complete recovery.If
untreated, only 10 to 20 percent will have a spontaneous
recovery and 80 percent will develop chronic heart disease.
For most children, recovery usually occurs within 2-3 months
from the onset of the illness.Of
the remaining one-third, 10 to 20 percent will improve but
have chronic residual heart problems called "dilated
cardiomyopathy."

This is a condition where the
heart has become enlarged and may have diminished function or
residual heart failure. In this case, the child will require
long term follow-up by a cardiologist Other children may
experience problems with the electrical conduction system
within the heart and are at risk for rhythm problems.A
common rhythm disturbance in this group is called heart block.
In its most severe form, heart block may result in a slow
heart rhythm that requires placement of a pacemaker.Other
irregular heart rhythms may also occur but are often
effectively treated with medications. The remaining 10 percent
will develop rapidly progressive disease with severe heart
failure.

The population that is at the
highest risk for serious disease is newborns. The mortality
rate is as high as 50 to 70 percent. When this is the case,
there is a high risk of sudden death and some children may
need a heart transplant urgently. This severity of disease is
rare and therefore represents a very small number of children.

adapted from the web site of the
Cincinnati Children's Heat Center and posted 07-07-05 on kidsgrowth.com

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advice and is not intended to replace the advice of your child’s
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